Process for delivering fuel and air to a rotary reduction kiln

ABSTRACT

A PROCESS AND APPARATUS ARE DISCLOSED FOR DELIVERING FUEL AND AIR TO A ROTARY REDUCTION KILN WHEREIN BOTH THE FUEL AND AIR ALTERNATELY FLOW THROUGH THE SAME NOZZLE.

Feb. 26, 1974 R0551 3,794,483

PROCESS FOR DELIVERING FUEL AND AIR TO A ROTARY REDUCTION KILN FiledOct. 51, 1972 2 Sheets-Sheet l Feb. 26, 1974 v RO$$| 3,794,483

PROCESS FOR DELIVERING FUEL AND AIR TO A ROTARY REDUCTION KILN FiledOct. 51, 1972 2 Sheets-Sheet 2 United States Patent Office 3,794,483Patented Feb. 26, 1974 3,794,483 PROCESS FOR DELIVERING FUEL AND AIR TOA ROTARY REDUCTION KILN Eugene F. Rossi, Wauwatosa, Wis., assignorfoAllis Chalmers Corporation, Milwaukee, Wis. Filed Oct. 31, 1972, Ser.No. 302,606

Int. Cl. C22]! 5/12 U.S. CI. 75-91 2 Claims ABSTRACT OF THE DISCLOSURE Aprocess and apparatus are disclosed for delivering fuel and air to arotary reduction kiln wherein both the fuel and air alternately flowthrough the same nozzle.

This invention relates to rotary kilns used for such purposes asreducing iron ore to a lower state of oxidation having nozzles mountedon the outer surface of the kiln projecting radially through the kilnshell for injecting air and fuel into the kiln at axially andcircumferentially spaced locations along the kiln length. In particularthe invention relates to such a rotary kiln wherein the same nozzle canbe utilized to alternately provide both the fuel and the air to the kilncharge.

In the prior art rotary kilns are known wherein a plurality of nozzlesare provided through the shell of the kiln to admit air and fuel intothe interior or ore reduction chamber of the kiln. A charge of ore isprovided in the reduction chamber and it is reduced to a higher state ofiron.

Examples of such prior art kilns are disclosed in U.S. patents 1,216,667issued Feb. 20, 1917, U.S. 2,091,850 issued Aug. 31, 1937 and U.S.3,182,980 issued May 11, 1965.

In the prior art kilns fuel and air are delivered through the nozzles bypiping supported on the exterior of the kiln or on the interior of thekiln. This piping is connected to the nozzles for injecting the fuel andair into the reduction chamber. In the prior art a mixture of both fueland air has been admitted through the nozzles at the same time or fuelis admitted through one nozzle and air admitted through a differentnozzle.

In certain instances it is desirable to admit only one fluid through anozzle when it is beneath the charge and only the other fluid when thenozzle is above the charge. As an example it is desirable in certaininstances to admit fuel to the reduction chamber through nozzles as theypass directly beneath the bed of the charge whereby the fuel flowsdirectly into the charge. When this nozzle has moved beyond the bed ofthe charge the fuel is shut off and no fluid is passing through thenozzle. At the same time air is admitted to the reduction chamber abovethe charge through additional nozzles. Before these air nozzles passbeneath the bed the air is turned off so that no fluid passes throughthese nozzles as they pass beneath the bed. From the above it can beseen that quite a large number of nozzles are required. It is notunusual to have as many as 300 nozzles in a rotary kiln of a 150 footsize. Further more these nozzles are exposed toextremely hightemperatures in the range of 2000 degrees Fahrenheit. While the fluid isflowing through a nozzle the fluid itself has a tendency to cool thenozzle. However when no fluid is passing through the nozzle itapproaches the temperature within the reduction chamber thereby reducingthe effective life of the nozzle.

It is therefore the intention and general object of this invention toprovide a process for reducing ore and apparatus for practicing theprocess wherein the number of nozzles required is reduced by one-halfand the temperature of the nozzles is reduced by admitting fluid throughthe nozzles during a substantial part of the kiln rotation.

An additional object of this invention is to provide a process whereinboth fuel and air are admitted through the same nozzles at differentpoints of rotation of the kiln.

A more specific object of the subject invention is to provide a processfor reducing ore of the hereinbefore described type wherein the fuel andair are admitted through the nozzle at a speed which is greater than thespeed of flame propagation of a combustible mixture of the fluid flowingthrouhg the nozzle.

Another object of the invention is to provide a process for a rotary orereducing kiln of the hereinbefore described type wherein the reducingfuel is admitted through a nozzle while the nozzle is beneath the orecharge and alternately air is admitted through the same nozzle while thenozzle is above the ore charge.

An additional object of the subject invention is to provide a rotarykiln with fluid distribution means which alternately delivers fuel orair to each nozzle at preselected points of rotation of the nozzlerelative to the kiln charge.

A more specific object of the subject invention is to provide a rotaryore reducing kiln of the hereinbefore described type wherein valve meansconnect both the fuel and air to a single nozzle for selective alternateflow of both fluids through the same nozzle.

An additional object of the subject invention is to provide a kiln ofthe hereinbefore described type wherein a single valve is utilized toalternately direct either fuel or air through the same nozzle atselected points of rotation of the kiln.

These and other objects of the subject invention will become more fullyapparent as the following description is read in light of the attacheddrawings wherein:

FIG. 1 is a side elevation of a portion of a kiln constructed inaccordance with the invention;

FIG. 2 is a section taken along the lines II--II of FIG. 1 andadditionally showing means for operating the fluid distribution means;

FIG. 3 is a cross-section of a particular type of valve showing oneinlet port connected to the outlet port;

FIG. 4 shows the same valve as FIG. 3 with both inlet ports shut off;and

FIG. 5 shows the same valve with the other inlet port connected to theoutlet port.

Referring to the attached drawing the kiln shown herein for purposes ofillustration is provided with an elongated cylindrical body portion 6which defines a cylindrical reduction or combustion chamber 7. The shellor inner wall 8 of the kiln may be constructed of any suitablerefractory material such as firebricks. Any well-known means may beprovided for supporting and rotating the kiln. Since such means form nopart of this invention and are well known in the art they are not shownherein. A charge of ore generally designated 9 is shown in FIG. 2. Amain burner 11 is provided at the right-hand end of the kiln to preheatthe kiln.

A plurality of circumferentially spaced and axially spaced nozzles 12are provided about the surface of the kiln opening into the chamber 7.These nozzles may be constructed of any conventional manner and arepreferably constructed in accordance with my co-pending applicationentitled Nozzle for Rotary Kiln. The nozzles may be supported by theouter kiln plate 13 in any conventional manner such as by welding. Aplurality of circumferentially spaced fuel and air conduits 14 and 16respectively are also supported about the surface of the kiln. Anyconventional means in the form of a manifold (not shown) may be providedto deliver fuel and air to the conduits 14 and 16.

A fluid distribution means generally designated 17 connects therespective fuel and air conduits to the associated nozzles. This fluiddistribution means may comprise a plurality of valves or as shown hereinfor purposes of illustration may comprise a single three-way 'valvegenerally designated 18 and fluid transfer conduit means 19 connectingthe outlet of the valve 18 to the associated nozzles 12. The particularvalve 18 shown herein for purposes of illustration is more clearlydefined in FIGS. 3 through 5. The valve consists of a valve body 20having two opposed inlet ports 21 and 22 and a single outlet port 23. Arotary plug 24 having a passageway 26 in the configuration shown isrotatably supported in the valve body and has a valve stem 27 attachedthereto and extending to the exterior of the valve body.

In many instances of reducing iron ore the fuel from conduit 14 isdelivered through the nozzles 12 while they are beneath the charge 9.Such fuel is only admitted while the nozzles are beneath the charge andair from conduit 16 is admitted through the same nozzles while they areabove the charge 9. To this end means are provided to operate the valve18 to effect this alternate delivery of fuel and air through each of thenozzles.

A preferred relatively inexpensive mechanical operating mechanism forcontrolling the flow of fuel and air into the chamber 7 is shown mostclearly in FIG. 2. It should be understood that while this controlmechanism is perfectly acceptable other means for operating the fluiddistribution means 17 could be employed such as a solenoid valveoperating hydraulic or air actuators. Referring to FIG. 2 a framegenerally designated 28 is provided about the kiln 6. This frame 28 isprovided with four strategically located trip means 29, 31, 32 and 33.

Each valve shaft 27 is connected to a cam plate 34 which is supportedfor rotation on brackets 36 connected to the exterior of the kiln forrotation therewith. Each cam plate 34 has four cams 37, 38, 39 and 41supported about the periphery thereof. The cams are spaced substantially90 degrees from one another and are located to engage a particular tripmeans when they are in the radially outermost position relative to theaxis of the kiln.

The operation of the apparatus will now be described. In order to assistin understanding the operation the trip means are identified on thedrawings starting with the trip 33 and progressing in the direction ofrotation of the kiln as air-oiffuel-onfuel-ofl and air-on. As a startingpoint assume that the cam 38 is about to contact the fuelon trip 29.This causes the valve 18 to move to the position shown in :FIG.connecting the fuel conduits 14 to the associated nozzles through thetransfer conduits 19. As the kiln continues to rotate the cam 39 willcontact the trip 31 and the valve 18 will be in the OE position shown inFIG. 4. As the kiln continues to rotate the cam 41 will contact the trip32 and the valve will be in the position shown in FIG. 3 permitting airto pass from the conduits 16 through the connected nozzles 12. Furtherrotation of the kiln causes cam 37 to contact trip 33 moving the valve18 to the opposite position as that shown in FIG. 4 interrupting theflow of air to the nozzles. This process of alternate admission of airand fuel through the nozzles will repeat as the kiln rotates.

From the above it can be seen that both fuel and air are alternatelyadmitted through each of the nozzles 12. This results in a reduction inthe number of nozzles required by one-half over those kilns which have aseparate nozzle for fuel and a separate nozzle for air. Furthermorebecause fuel or air is flowing through each nozzle during a substantialpart of the revolution of the kiln the nozzle temperature is reduced dueto the relatively cooler fuel or air passing through the pipes on theexterior of the kiln. It should be understood that the control mechanismcould be so arranged that the air flowing through the nozzle is onlyturned off as the fuel is turned on thereby having no period of timethat a fluid is not flowing through the nozzles.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A process for reducing a charge of ore in a rotating kiln havingnozzles open to the interior of the kiln comprising the steps of:

(a) delivering a reducing fluid through those nozzles that are beneathsaid charge at a speed greater than the speed of flame propagation of acombustible mixture of said reducing fluid and an oxidizing fluid;

(b) interrupting the flow of said first fluid through said nozzles whenthey are no longer beneath said charge;

(0) delivering an oxidizing fluid through said nozzles when they areabove said charge;

((1) interrupting the flow of said oxidizing fluid through said nozzleswhen they are again beneath said charge; and

repeating steps (a) through (d) while the reduction process continueswhereby the temperature of said nozzles is lowered because of thepassage therethrough of said reducing fluid and said oxidizing fluidduring a substantial part of the kiln rotation.

2. The process according to claim 1 wherein said reducing fluid is areducing gas and said oxidizing fluid is air.

References Cited UNITED STATES PATENTS 2,091,850 8/1937 GOhIe 432-109 XALLEN B. CURTIS, Primary Examiner J. F. NIEBLING Assistant Examiner U.S.Cl. X.R.

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,794,483 Dated February 26, 1974 lnventoflg Encrene F. -Rossi It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 4, line 29, "first" should read reducing Signed and sealed this2nd day of July 1974' '(SEAL) Attest: v H

EDWARD M. FLETCHER,JR. C.'MARSHALL DANN I Attesting Officer Commissionerof Patents

